Oil circuit breaker control mechanism



Aug. 18, 1936. F. H. COLE ET Al. 2,051,244

OIL CIRCUIT BREAKER CONTROL MECHANISM Filed'July 28, 1932 2 sheets-sheet 1 Aug. 18, 1936.

F. H. COLE ET AL OIL CIRCUIT BREAKER CONTROL MECHANISM Filed July 28, 1932 2 Sheets-Shee?l 2 Cil Patented Aug. 18, 1936 UNITED STATES PATENT GFFICE OIL CIRCUIT BREAKER CONTROL MECHANSM nois Application July 28, 1932, Serial No. 625,428

13 Claims.

This invention relates to= electric circuit breakers in general, and more particularly to the operating and tripping means for high voltage circuit breakers or for breakers of vhigh current interrupting capacity.

Circuit breakers of the kind here contemplated, when considered in connection with their operating mechanism, are generally provided with some means, in the form of stiff springs or the like, for continuously urging the mechanism to the open position. A link mechanism is provided for retaining the mechanism in its closed position, said link mechanism being held in place by a latch or the like. The link mechanism is so arranged that a tremendously large force or bias exerted thereon will be overcome or balanced by an exceedingly small reaction on the latch,

whereby the latch may be easily and quickly tripped to release the link mechanism to instantly open the circuit breaker. This involves a delicacy of action and balance which is exceedingly difficult to maintain, especially after the circuit breaker has been in use for some time. It is one of the objects of the present invention to provide an improved release mechanism that is proof against accidental release by vibration or the like. We accomplish this end by mounting the trip mechanism separate from the switch operating mechanism so that the trip mechanism does not move as a unit with the operating mechanism during the switch closing operation. By this arrangement the trip mechanism is not subject to vibration during the closing operation and is not likely to cause a false release of the mechanism during the switch closure. By this same arrangement we obtain another advantage in that the circuit breaker can not be even partially operated as long as the trip mechanism is in its tripping position. In most switch operating mechanism of the type wherein the tripping latch is mounted on and movable with one of the links that effects the switch closure it is possible to produce a substantial operation of the mechanism while the release magnet is energized, and not until the latch carrying link approaches its switch closed position is the latch released to trip the mechanism and prevent closing of ythe breaker. By mounting the trip-ping mechanism about stationary pivots said mechanism is released by the tripping magnet independent of the instantaneous position of the switch operating mechanism, hence it is not necessary to operate the switch actuating mechanism any substantial amount to bring about a release of the tripping means.

The switch tripping mechanism of the present (Cl. 20G-109) invention is so constructed as to be able to resist a comparatively great thrust tending to open the switch operating mechanism and yet to require a negligible actuating force to bring about tripping of the mechanism. 'This satises the desirable requirement that there be available a great force to open the breaker whereby a high initial acceleration of the contacts is obtained to produce a high velocity of separation to quickly open the circuit. On the other hand, it is also desirable that the trip mechanism be sensitive toa slight force applied to the tripping portion thereof. The trip mechanism is arranged to be tripped by an electromagnet which is connected to be responsive to predetermined circuit conditions such as overload, short circuit, unbalanced current flow, reverse power flow, or the like. Under normal conditions the tripping magnet is not energized. The energization commences upon the closure of the magnet circuit and the less force that is required to trip the mechanism the less work the magnet will have to do and the quicker it will be done. Hence by the present invention there is obtained a very rapid acting trip mechanism. In the embodiment of the invention herein illustrated this is obtained by pivoting a release lever about a stationary pivot and providing the same with a cam member that resists the relatively great opening force of the operating mechanism. The release lever is urged to its release position by the operating mechanism which furnishes the energy required to move it to its release position. A toggle holds the release lever against releasing the mechanism, said toggle being Vurged to its collapsed position by the force of the operating mechanism transmitted through the release lever, and being locked against collapse by a trip catch. A great mechanical leverage is obtained between the trip catch and the toggle, while the toggle itself has a great mechanical leverage in resisting the force on the release lever. By this arrangement a very great force applied to the release lever by the switch operating mechanism can be resisted by a very small force on the trip catch. Therefore only a very small force need be applied by the tripping magnet to actuate the trip catch to release the trip mechanism to permit tripping of the circuit breaker.

In order to reduce the friction between the moving parts of the trip mechanism and thus further reduce the pressure that must be applied to the trip catch to release the same we provide non-wearing cams and rollers wherever there is a relative sliding action between two members. This overcomes another disadvantage inherent in similar mechanisms of the prior art wherein a high degree ot sensitivity is required. At the time the switch mechanism leaves the factory and is installed in service the various parts are in accurate adjustment whereby the desired leverages are obtained. After the mechanism has been in service for a period of time there may be considerable wear between certain parts. In a mechanism wherein tremendous mechanical advantages are obtained by the use of comparatively short levers some of which are arranged to constitute parts of toggles even a slight wear on certain members will produce an appreciable angular difference between members of a toggle, resulting in great diiferences in the mechanical leverages obtained. By providing non-Wearing cams and rollers at the critical places in the mechanism such variations do not occur and the mechanism retains its same degree of sensitivity even after long periods of use.

The attainment of the above and further objects of the present invention will be apparent from the following specication taken in conjunction with the accompanying drawings forming a part thereof.

In the drawings:

Figure 1 is a side view of the switch operating mechanism of the present invention showing the various parts in the switch closed position, the reverse trip attachment being omitted for the sake of clarity;

Figure 2 is a side view of one of the links shown in Figure 1;

Figure 3 is an enlarged view of the trip mechanism in Figure 1; and

Figure 4 is a sectional view taken along the line 9--9 of Figure 3 and looking in the direction of the arrows.

Referring now more particularlyv to the drawings the switch operating mechanism comprises a series of links for actuating and releasing a switch, a trip mechanism indicated in general. by the reference numeral 2 for holding the mechanism in its switch closed position and for permitting tripping thereof under predetermined conditions, a spring 3 for moving the mechanism to the open position upon release thereof by the trip mechanism, a resetting spring 4 for conditioning the mechanism for reclosure after the same has opened to its operating position and an electromagnet 5 for actuating the mechanism to its switch closed position.

The various links, springs, electromagnets, etc. are mounted upon a support Ii! including a pair of arms II-H at one end thereof and another pair of arms i2-I2 for supporting the various operating mechanisms. An operating shaft I4 is rotatably mounted between the arms I I-I I and comprises a support for a latch member I5 that is mounted thereon but freely rotatable with respect thereto so that upon rotation of the shaft I4 the latch does not rotate. The latch comprises two similar members on opposite sides of the longitudinal center of the mechanism each including a link or lever portion IG that extends one one side of the shaft and integrally therewith an arm il that extends on the other side of the shaft. A catch member I9 is pivoted to the arm I Il about a stationary pivot pin 2E) and is biased to the position shown in Figure l by means of a spring 2l. The catch is provided with an arm 22 :formed integrally therewith for actuating the catch in a counterclockwise direction to move the same to its release position. The arm 22 carries a roller 23 at the end thereof that cooperates with a cam surface M for moving the arm 22 and with it the entire catch about the pivot 25 to its released position. The cam surface 24 is formed on an arm that is integral with a lever 25 'that is also supported on the shaft ifi and is rotatable with respect thereto independent of actuation of the shaft I4. More will be said of the lever 25 as the description proceeds.

A link 2l is pivoted to the arm I 6 of the latch about a pivot pin 28. At its opposite end the link 2l is pivotally connected to a lever 29 by means of a pin 35i. The lever 29 is pivoted about a pin 3l that extends between the arms l 2. The spring urges the lever Z9 in a clockwise direction about the stationary pin SI said movement being opposed by the link 27, the latch I5, and the catch i9 when the switch is in its closed position. The lever 29 comprises two identical members both of which are pivoted about the pin 3l and are connected together at their opposite ends by the pin 35 and intermediate thereto by two pins 32 and 33. The pin 32 extends between the two lever arms 29--29 and carries a support 35 for the end of the spring 4l. The pin 33 comprises a support for 5a plunger rod 38 of the electromagnet 5 and it also comprises a support for a bell crank link @Il shown more particularly in Figure 4. The lever 40 comprises l a pair of arms Ill-li joined by a web portion i2 and has a bushing I3 extending outwardly from one of the arms 4I and a bushingrll extending outwardly from the other arm 4I, both of said bushings being integral with the arms fii-ii- Said bushings comprise supports for the pivot pin 33. The bushing lill has an arm #i5 integral therewith, said arm being therefore integral with the arms ii-QI. The lever l5 extends under the catch of the trip mechanism 2 and when the mechanism is locked against release, as will be hereafter more fully set forth, is held against upward movement. A link 5I) is pivoted between the arms 4I-4I by means of a pin 5I and, at its opposite end, it is pivotally connected to the levers 25-25 by means of a pin 52. The levers 25-25 are, as previously stated, supported at the one end by the shaft t@ but rotatable with respect to the shaft so that they may rotate independent of the shaft rotation. At their opposite ends the levers 25-25 are pivotally connected to an eye bolt 55 by means of a pin 55. The eye bolt has connected thereto at its opposite end an accelerating spring head 58 that is vertically movable and is guided 1cetween three accelerating spring guide rods Sii-59. The spring 3 exerts an upward thrust upon the head 58 tending to move the eye bolt 55 upwardly to rotate the link 25 about the shaft lli. A circuit breaker operating rod 60 that eX- tends to a circuit breaker mechanism is pivotally connected to the link members 25 through a clevis 6I and a pin 62. As long as the links 25 are held against upward movement from the position shown in Figure 1 the circuit breaker is held against opening. When the circuit breaker is in its open position a downward movement of the links 25 brings about a downward movement of the rod 6I) to close the circuit breaker.

It is to be noted that the spring 3 continuously exerts an upward force upon the links 25 tending to move those links in a counterclockwise direction as seen in Figure 1 to open the circuit breaker. This exerts an upward force on the link 55 which tends to rotate the arms 4I of the 75 link 40 in acounterclockwise direction about the pivot pin 33. As long as the arm 45 is held at its outer end against movement, the link 40- cannot rotate about the pin 33 as a center. The trip mechanism 2 holds the lever arm 45 against such movement. The arms 1I- 4|` of the link 40 therefore exert an Vupward force upon the pin 33 which force, together with the force of the spring 4, tends to rotate the levers 29 about the pin 3| as a center. As long as the latch I5' is held against'counterclockwise movement by the catch 0 the pivot pin 30 cannot move upwardly since the link 21 connects this pin with the pin` 28 on thearm I6 of thelatch. Therefore the link 2T locks the arm 29 against upward movement .about the pin 3| as a center.

It is to be noted that the arms 4 I of the bell crank 40 form an overlapping toggle with the link 50 since the pins 33, 52 and 50 are substantially in alignment. Therefore as long as the pin 33 is maintained stationary a comparatively large upward forcevtransmitted from the pin 52 through the link 50 to the pin 5| has avery exceedingly small component in a directionV at right angles to a line joining the centers of the pins 33 and 5|, that is, in a ldirection tending to rotate the arms 4| about the pin 33 as a center. Since this component of the force tendingl to rotate the arms 4| in a counterclockwise direction is resisted by the trip mechanism 2 acting at the outer end of the lever 45 that is of appreciable greater length than the arms 4|, it follows that only an exceedingly small resistance force on the trip mechanism will hold the lever 45 against rotation about the pin 33-and thereby hold the link 45 against upward move-V ment. A tremendous mechanical vadvantage is thus obtained whereby a very small force on the trip mechanism is able to hold the operating mechanism against releasing the switch under the action of the very powerful spring 3.

Manual means is also provided for operating the mechanism to the switch closed position in lieu of energization of the magnet 5. This manual means comprises a lever 12 that is clamped to the shaft I4 to be rotated thereby. The lever 12 bears against the arm |6 Vof the'latch |5 so that upon clockwise rotation of the shaft I4 from its switch open position the lever 12 bears against the arm I6 and rotates the same into the position shown in Figure l. A spring bumper is provided for limiting the extent of motion ofthe link 21 in its switch closing direction. Thiscomprises a spring 15 carried by an arm 16 that isV a part of the frame I0. An operating handle may be detachably secured to the' extended end of the shaft I4 to rotate the same to actuate the mechanism to its switch closed position.

Y The vtrip mechanism shown more particularly in Figures 3 and 4 comprises a carriage |0I that is bolted or otherwise rigidly secured to the frame A pair of plate-like ear 'members' |02-V-I02 are formed integrally with the carriage and constitute a support for various pivot pins about which the trip links pivot. A trip link |04 is pvoted between the ears by means of a pin |05 and is biased to the position shown in Figure 3 by a coiled spring |06. VThe trip link has an upward and forwardly extending arm |01 formed integrally therewith and comprisingv a support for trip cam |08 pivoted to the trip link about'a pivot pin |09. A spring biases the trip cam to the position shown in Figure `3, said spring extending between an armV I|2 formed integrally with the trip link |04 and an arm VI I3 formed integrally with. the trip cam |08. A stop I|4, which comprises a part of the trip cam, limitsl the extent of rotation of the trip cam about the pin |09 under the action of the springl Another stop H5, also formed integrally with the trip cam, limits the extent of rotation of this cam in the opposite direction, that is counterclockwise about the pin |09. A roller ||6 is pivoted to the trip cam v|08 and ridesv on the end of the lever 45. A toggle comprising a link |20 and a link: |2| pivoted together at |22 extends between the trip link |04 and a stationary pivot |23. The link |20 is pvoted to the trip link by means. of a pivot pin |25. A release catch |26 Vis pivoted about the pivot |23 and is maintained in the position shown in Figure 3 by means of a spring |28. The pivot for the release catch is shown as coincident with the stationary pivot for the link |2| although the two pivots may be spaced apart without departing from the spirit of the present invention. 'Ihe release catch includes a cam portion |30 on one side of the pivot |23 and a pair of spaced arms |3| on the other side of the pivot pin |23. A roller |32 is mounted between the arms |3|-|3|.

The link |20 of the toggle |20-I2I includes an arm |35 formed integrally therewith and extending beyond the knuckle |22 of the toggle. The lower end of the arm |35 extends between the two arms |3|-|3| of the release catch and is held therein by the roller |32. A trip lever |40 is rigidly mounted upon a rotatable pin |4| that is mounted between the arms |02|02 of the trip carriage. The trip lever includes a cam face |42 that cooperates with the face |30 of the release catch. A tripping magnet |45 is provided for the purpose of actuating the trip lever to actuate the release catch to release the trip mechanism. For this purpose the electromagnet is provided with a plunger |48 which, upon energization of the magnet, rises and through the trip lever produces clockwise rotation of the release catchA |26. The pin or rod |4| extends along the end of the carriage |0| and, at the end thereof, has a lever |50 secured thereto and carrying a roller |5|. The lever |50Va1so has an arm |52 extending therefrom. The lever |50 is provided for tripping the mechanism independently of the electromagnet 45, that is either for manual tripping or for tripping under predetermined conditions during the closing operation of the mechanism, as will be more fully set forth as this description proceeds. In those cases where it is not desired to provide for tripping the mechanismY by means other than the tripping magnet |45 the lever |50 and the pin or rod |4| and the trip lever |40 are all omitted, the electromagnet plunger |48 being then arranged to directly contact with the release catch |26.

An explanation will now be given to the mode of operation of the tripping mechanism. When the switch is closed the various parts are in the positions shown in Figure 3. The lever 45 at this time exerts an upward thrust on the roller ||6 tending to rotate the same about the pin |09. Since the trip cam |08 is now in its extreme position ywith respect to the trip link |04 by reason of the fact that the stop I |4 engages the arm |01, such rotation of the trip cam cannet take place. Therefore, the thrustvis transmitted through the pin |00 and tends to rotate the trip link |04 about the pin |05 as aI center. This is resisted first by the spring |05 and secondly by the toggle |20-|2|. The spring, |06 is a comparatively light spring and is incapable of opposing clockwise rotation of the trip link v|04 about theV pin |55V under theaction of the thrust of the lever 45 upon the roller i6. However,- such rotation ispositively prevented by the toggle |20-I 2| since the arm |35 of the link |25 is held against movement to the right as seen in Figure 3 by the roller |32.' Therefore, the mechanism is positively locked in position. No amount of thrust by the lever i5 can move the trip link |54 to the right as seen in Figure 3, because of this toggle. If the release catch |26 is rotated in a clockwise direction, as by manual operation of the trip lever 48, or b-y the plunger `|48 upon energization ofthe tripping magnet |45, the roller |32 moves downward and out'of the path of movement of the link E35. The toggle |2|2| is now free to release to permit movement of the knuckle |22 thereof in a -generally clo-ckwise direction about the pivot |23. This permits rotation of the trip link |54 under the action of the thrust transmitted thereto by the lever 45, which thrust is suflicient to overcome the opposite force of the torsion spring |65.' Therefore, the trip link |04 rotates to theV position indicated in dotted lines in Figure 3 and permitsV the lever 45'to move past the-roller HS. During the rotation of the trip link the roller HG rolls on the upper surface of the .lever 45. When the trip link |54 is in the position shown in" dotted lines in Figure 3 the toggle '|2l-|2|`is in the position also indicated by the dotted lines. WhenV the lever 45 rides past the roller H6 there is no longer a force on the trip link tending to hold it in its dotted line position and therefore the spring |56 moves the trip link back to its original position. As it moves back to its original position it returns the toggle |2El|2| to its original position. If the release catch has been previously released the lower end of the arm |35 will ride over the roller |32 and momentarily push that roller downward to permit the arm to assume the position shown. Immediately thereafter the spring |28 restores the release catch |25 to the position shown. If the release catch has not been previously released by the electromagnet the arm |35 will nevertheess assume the position shown but the toggle mechanism will not become locked until the release catch is restored by the spring |28, and the roller |32 again abuts against the end of the arm |25. The trip mechanism is now again locked in position. When the lever 45 moves downwardly during the resetting operation of the switch mechanismthe surfacel l thereof rides on the roller I6 and vforces the trip cam |88 in a counterclockwise direction about the pin |09 to permit the lever '45 to assume the position shown. As soon as the end of the lever 45 rides past the roller the spring immediately restores the trip cam |58 to the. position shown in full lines in Figure 3. It is to be noted that during such resetting operation the trip link |84 is locked by the toggle S29-VM against clockwise rotation about the pin |55. This, however, does not prevent counterclockwise rotation of the trip cam |08 about the pin |59. When the lever 45 thus assumes the position shown the mechanism is again restored and ready for the closing operation. During the closing operation it is essential that the end of the lever 45 be held against upward movement. AThis is accomplished by the trip cam E58 which cannot rotate in a clockwise direction about its pin |59 due to the stop H4, and which cannot move about the pin as a center to release the lever 45 due to the fact that the' toggle mechanism holds the trip link against such motion. If, however, an attempt is made to close vthe switch operating mechanism when the release catch |26 is not in its locking position it is apparent that the upward thrust on the lever 45 will force the trip mechanism back and permit release of the lever 45.

f In connection with the trip mechanism here shown attention is called to the fact that the vital parts of the mechanism move about two stationary pivots and that no motion is required of the trip mechanism during the closing of the switch. Attention is further called to the fact that where various parts are required to roll on one another anti friction rollers are provided. By this arrangement it is possible to provide an exceedingly powerful spring 3 for quickly accelerating the opening movement of the switch contacts and yet require an'exceedingly small tripping force of the tripping magnet |45 to bring about tripping of the latch 2. Attention is further called to the fact that the force required to move the tripping mechanism to its disengaging position is not supplied by the electromagnet |45. This force is supplied by the lever 45 acting on the roller I6 of the tripping mechanism. By this arrangement an exceedingly small forcey is required of the electromagnet to actuate the release catch |26 to release the mechanism although a rather tremendous force is available at the spring 3 for quickly releasing the mechanism and moving the same to its open position. Y

In compliance with the requirements of the patent statutes we have herein shown and described a preferred embodiment of our invention. It is, however, to be understood that the invention is not limited to the precise arrangement herein shown, the same being merely illustrative of the general principles of our invention. What we consider new and desire to secure by Letters Patent is:

1. Locking means for switch operating mechanism comprising a pivoted link, stop means for limiting the extent of movement of the link in one direction, a switch locking cam pivoted on the link and including roller means for receiving the thrust of the switch operating mechanism and urging the link in the opposite direction, a toggle locking the link against movement in said opposite direction, one of the links of the toggle being extended beyond the knuckle of the toggle, and a releasable latch holding said extended portion of the toggle to hold the knuckle of the toggle against breaking.

2. Locking means for switch operating mechanism comprising a pivotedlink, stop means for limiting the extent of movement of the link in one direction, a switch locking cam pivoted on the link and including roller means for receiving the thrust of the switchV operating mechanism and urging the link in the opposite direction, a toggle locking the link against movement in said opposite direction, one of the links of the toggle being extended beyond the knuckle of the toggle, a releasable latch holding said extended portion of the toggle to hold the knuckle of the toggle against breaking, and electromagnetic means for releasing the latch to release the toggle to permit movement of the link in said opposite direction under the thrust force on the switch locking cam, thereby moving the cam out of locking position, and spring means for restoring the link.

3. A switch trip mechanism comprising a link pivoted on astationary pivot, a cam pivoted on said link,l a limiting stop limiting the V,extent of movement of the cam about its pivot on the link, spring means for maintaining the cam in its limiting position whereby a thrust on the cam in one direction forces it about its pivot on the link while a thrust in the opposite direction Yforces the cam and the link as a unitary body about the stationary pivot, a toggle resisting the motion of the link about its pivot, and a trip catch for releasably holding said toggle against breaking.

4. A switch trip mechanism lcomprising a link pivoted on a stationary pivot, a cam pivoted on said link, a limiting stop limiting the extent'of movement ofthe cam about its pivot on the link, spring means for maintaining the cam inV its limiting position whereby a thrust on the cam in one direction forces Vit about its pivot on the link while a thrust in the opposite direction forces the cam and the link as a unitary body about the stationary pivot, a toggle resisting the motion of the link about its pivot, a trip catch for releasably holding said toggle against breaking, means for biasing the trip catch to its holding position, and spring means for restoring the link and the toggle to the locked position upon the release of the thrust on the cam.

5. A switch trip mechanism comprising a link pivoted on a stationary pivot, a cam pivoted on said link, a limiting stop limiting the extent of movement of the cam about its pivot on the link, spring means for maintaining the cam in its limiting position whereby a thrust on the cam in one direction forces it about its pivot on the link while a thrust in the opposite direction forces the cam and the link as a unitary body about the stationary pivot, a toggle resisting the motion of the link about its pivot, one member of the toggle being extended beyond the knuckle of the toggle, and a release catch for releasably holding the extended portion of the toggle to hold the toggle against breaking."

6. A switch trip mechanism comprising a link pivoted on a stationary pivot, a cam pivoted on said link, a limiting stop limiting the extent of movement of the cam about its pivot on the link, spring means for maintaining the cam in its limiting position whereby a thrust on the cam in one direction forces it about its pivot on the link while a thrust in the opposite direction forces the cam and the link as a unitary body about the stationary pivot, a toggle resisting the motion of the link about its pivot, one member of the toggle being extended beyond the knuckle of the toggle, and a release catch for releasably holding the extended portion o the toggle to hold the toggle against breaking, said release catch having a roller at one end having rolling engagement with said extended portion.

'7. In combination with a switch operating mechanism including a lever controlling the stability of the mechanism, the end of said lever being urged in a given direction when the switch is closed, a trip mechanism for holding the end of the lever and for releasing the same under predetermined conditions, said mechanism including a stationary supporting structure, a link pivoted thereon, spring means urging the link to its limiting position, toggle means controlling return movement ci the link from its limiting position, a releasable catch for holding the toggle against breaking, a trip cam pivoted on the link and having a limited movement about its pivot, spring means maintaining the trip cam in its limiting position on the link, said trip cam bearing against the' end of the 'rstnamed le'ver and holding `the same against release, the thrust of the lever on the cam being in a direction to maintain the trip cam in itsv limiting position Awhereby the -thrust is transmitted through the trip cam to the link to urge the link about its pivot, the force transmitted to the link from the leverfbeing superior to'the force of the first named spring whereby upon release of the toggle therst named link is swung about its pivot to permit release ofV the lever, said iirst named'spring restoring the link and the toggle upon release of the lever. Y

V8. In combinationwith -a switch operating mechanism lbiased-to its open position and including a series of links movable for actuating the switch, a` tripping device forvreleasably lock- VingV the mechanism in its closed position, said tripping device comprising a unit separate from thev operating mechanism andincluding a member bearing against the mechanism and urged thereby to its unlocked position, and means including a toggle pivoted about a stationary pivot and holding the said member against release, whereby upon release of the toggle the mechanism forces the member to its unlocked position to permit tripping of the mechanism.

9. In combination with a switch operating mechanism including a lever controlling the stability of the mechanism, the end of said lever being urged in a given direction when the switch is closed, a trip mechanism for holding the end of the lever and for releasing the same under predetermined conditions, said mechanism comprising a link pivoted about a stationary pivot, u

toggle means for controlling the movement of the link, electromagnetically controlled means for holding the toggle means against breaking, a switch locking cam pivoted on the link and urged about its pivot by the lever, stop means preventing movement of the cam means about its pivot in the direction urged by the lever, whereby the cam means holds the lever, said cam means swinging as a unit with the link upon release of the toggle to release the lever, and means for restoring the link, cam means, and toggle to the locking position independently of the restoration of the lever, said cam means turning about its pivot on the link under the action of the lever upon restoration of the lever.

10. A switch trip mechanism comprising a link pivoted about a stationary pivot, toggle means for controlling the movement of the link, electromagnetically controlled means for holding the toggle means against breaking, a switch locking cam pivoted on the link and free to move as a unit with the link, said cam moving as a unit with the link upon release of the toggle to trip the mechanism, means for restoring the link, the toggle means, and the locking cam to their locking positions independently of the toggle holding means, said locking cam being thereafter swingable about its pivot on the link.

l1. A switch tripping mechanism comprising a .stationary supporting carriage, a link pivoted thereto, a switch locking cam lever pivoted to one end of said link, integral stop means on said cam lever for preventing its rotation in one direction to transmit the thrust of the switch mechanism to said link, resilient means providing rotation of said lever about said link in the opposite direction for resetting said tripping mechanism, and releasable means engaging said link for restraining it from movement due to said thrust.

. 12. The combination with aswitch mechanism normally urged toward tripping position, of a trip mechanism therefor comprising a stationary supporting carriage, means pivotally supported on said carriage, a locking cam lever pivotally mounted on one end of said means and having an integral stop member engaging said means to prevent rotation of said lever in one direction for transmitting thrust of said switch mechanism to said link, said lever being rotatable in the opposite direction upon resetting of said switch mechanism, means for restraining said pivotal supported means from movement due to transmission of said thrust thereto, and means for releasing said restraining means to trip said switch mechanism.

13. A switch tripping mechanism comprising a stationary pivot, a link rotatable thereabout, spring means urging said link in one direction,

toggle vmeans limiting movement of said link in said direction, a switch locking cam pivoted to said link, stop means on said cam for limiting its rotation in switch tripping direction with respect to said link to'transmit the thrust of the 

